Patent EP0693835A2 successfully refreshed from Google Patents.
US4180841A
Expired / Lapsed
US
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Ground fault circuit interrupter with grounded neutral protection
Assignee: Westinghouse Electric Corp
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Filing: 1977-11-21
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Granted: 1979-12-25
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Expires: 1997-11-21
Abstract
Abstract A ground fault circuit interrupter includes a differential current transformer sensing winding supplying input to an integrator which is reset to zero at the end of each half-cycle of AC line current. A line-to-ground fault current will cause the integrator output to exceed a predetermined limit value and produce a trip indication. A saturable neutral transformer supplies a voltage to the neutral line and a reference current proportional to the neutral voltage to a comparator. The peak value of the reference current is compared to the peak value of the sensing winding output. A low-resistance neutral-to-ground path causes the sensing winding output to exceed the reference current and a signal to be added to the integrator input, thereby producing a trip indication which energizes an SCR to activate a solenoid. Means are provided to produce a positive feedback signal to insure a "hard" turn-on of the SCR upon receipt of a trip indication, the feedback means also including capability to "remember" a trip indication at the end of a half-cycle near current zero, and to produce the positive feedback signal at the beginning of the next succeeding half cycle.
Inventors
- 👤 Joseph C. Engel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 11:28
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/26; H02H3/32; H02H3/33; H02H3/331
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
175 words
A ground fault protective apparatus for use on an AC electrical circuit having a line conductor and a neutral conductor grounded at a power source, comprising: means for sensing current imbalance on said line and neutral conductors, said sensing means providing an output signal proportional to said imbalance; means for integrating said output signal and for providing a trip indication whenever said signal integration value exceeds a predetermined reference level; means for inducing a test voltage on said neutral conductor, whereby a current imbalance is produced between said line and neutral conductors which is proportional to the neutral-to-ground conductance; means for providing a reference current proportional to said test voltage; means connected to the input of said integrating means for comparing said reference current to the output signal of said sensing means, said comparing means supplying a signal current to the input of said integrator whenever the output signal of said sensing means rises above said reference current, said signal current being of sufficient amplitude to cause said integrator means to produce a trip indication.
Claim 2
Dependent Claim
175 words
A ground fault protective apparatus for use on an AC electrical circuit having a line conductor and a neutral conductor grounded at a power source, comprising: means for sensing current imbalance on said line and neutral conductors, said sensing means providing an output signal proportional to said imbalance; means for integrating said output signal and for providing a trip indication whenever said signal integration value exceeds a predetermined reference level; means for inducing a test voltage on said neutral conductor, whereby a current imbalance is produced between said line and neutral conductors which is proportional to the neutral-to-ground conductance; means for providing a reference current proportional to said test voltage; means connected to the input of said integrating means for comparing said reference current to the output signal of said sensing means, said comparing means supplying a signal current to the input of said integrator whenever the output signal of said sensing means rises above said reference current, said signal current being of sufficient amplitude to cause said integrator means to produce a trip indication.
Claim 3
Dependent Claim
19 words
Apparatus as recited in claim 1 wherein said test voltage inducing means produces voltage pulses upon said neutral conductor.
Claim 4
Dependent Claim
40 words
Apparatus as recited in claim 2 wherein the peak value of said reference current is proportional to said test voltage and said comparing means compares the value of said reference current with the value of said sensing means output current.
Claim 5
Dependent Claim
32 words
Apparatus as recited in claim 3 wherein said reference current has an instantaneous value proportional to said induced voltage pulses, and a faster rise and decay time than said induced voltage pulses.
Claim 6
Dependent Claim
23 words
Apparatus as recited in claim 1 wherein said integrating means is reset every half cycle of frequency upon said line and neutral conductors.
Claim 7
Dependent Claim
110 words
Ground fault protective apparatus for use on an AC electrical circuit having a line conductor and a neutral conductor, comprising: means for sensing current imbalance on said line and neutral conductors, said sensing means providing an output signal proportional to said imbalance; means for integrating said output signal; means connected to said integrating means for providing a trip indication whenever the output of said intergating means exceeds a predetermined reference; means for resetting said integrating means after each half cycle of said AC electrical circuit; and means for generating a feedback signal to the input of said integrating means when the output of said integrating means exceeds a predetermined level.
Claim 8
Dependent Claim
110 words
Ground fault protective apparatus for use on an AC electrical circuit having a line conductor and a neutral conductor, comprising: means for sensing current imbalance on said line and neutral conductors, said sensing means providing an output signal proportional to said imbalance; means for integrating said output signal; means connected to said integrating means for providing a trip indication whenever the output of said intergating means exceeds a predetermined reference; means for resetting said integrating means after each half cycle of said AC electrical circuit; and means for generating a feedback signal to the input of said integrating means when the output of said integrating means exceeds a predetermined level.
Claim 9
Dependent Claim
172 words
Ground fault protective apparatus for use on an AC electrical circuit having a line conductor and a neutral conductor, comprising: means for sensing current imbalance on said line and neutral conductors, said sensing means providing an output signal proportional to said imbalance; means for integrating said output signal; means connected to said integrating means for providing a trip indication whenever the output of said integrating means exceeds a predetermined reference; and means for resetting said integrating means after each half cycle of said AC electrical circuit; said trip indicating means comprising a switching device having an input terminal connected to said integrating means and an output circuit operable between open and closed positions in response to said input terminal, said apparatus comprising memory means connected to said input terminal for maintaining electrical parameters produced at said input terminal when said integrating means output exceeds said predetermined reference, whereby said switching device output terminals are maintained in the closed position for a period exceeding one half cycle on said line and neutral conductors.
Claim 10
Dependent Claim
172 words
Ground fault protective apparatus for use on an AC electrical circuit having a line conductor and a neutral conductor, comprising: means for sensing current imbalance on said line and neutral conductors, said sensing means providing an output signal proportional to said imbalance; means for integrating said output signal; means connected to said integrating means for providing a trip indication whenever the output of said integrating means exceeds a predetermined reference; and means for resetting said integrating means after each half cycle of said AC electrical circuit; said trip indicating means comprising a switching device having an input terminal connected to said integrating means and an output circuit operable between open and closed positions in response to said input terminal, said apparatus comprising memory means connected to said input terminal for maintaining electrical parameters produced at said input terminal when said integrating means output exceeds said predetermined reference, whereby said switching device output terminals are maintained in the closed position for a period exceeding one half cycle on said line and neutral conductors.
Claim 11
Dependent Claim
22 words
Apparatus as recited in claim 7 wherein said switching device comprises a silicon controlled rectifier and said memory means comprises a capacitor.
Claim 12
Dependent Claim
27 words
Apparatus as recited in claim 7 comprising means connected to said memory means and the input of said integrating means for generating a positive feedback signal therebetween.
Claim 13
Dependent Claim
22 words
Apparatus as recited in claim 9 wherein said switching means comprises a silicon controlled rectifier and said memory means comprises a capacitor.
Claim 14
Dependent Claim
95 words
Ground fault protective apparatus for use on an AC electrical circuit having a line conductor and a neutral conductor, comprising: means for sensing current imbalance on said line and neutral conductors, said sensing means providing an output signal proportional to said imbalance; means for integrating said output signal; means connected to said integrating means for providing a trip indication whenever the output of said integrating means exceeds a predetermined reference; and means for generating a feedback signal to the input of said integrating means when the output of said integrating means exceeds a predetermined level.
Claim 15
Dependent Claim
95 words
Ground fault protective apparatus for use on an AC electrical circuit having a line conductor and a neutral conductor, comprising: means for sensing current imbalance on said line and neutral conductors, said sensing means providing an output signal proportional to said imbalance; means for integrating said output signal; means connected to said integrating means for providing a trip indication whenever the output of said integrating means exceeds a predetermined reference; and means for generating a feedback signal to the input of said integrating means when the output of said integrating means exceeds a predetermined level.
Claim 16
Dependent Claim
141 words
Ground fault protective apparatus for use on an AC electrical circuit having a line conductor and a neutral conductor, comprising: means for sensing current imbalance on said line and neutral conductors, said sensing means providing an output signal proportional to said imbalance; means for integrating said output signal; first trip means connected to said integrating means for providing a trip indication whenever the output of said integrating means exceeds a predetermined reference; means for inducing a test voltage upon said neutral conductor, whereby a current imbalance is produced between said line and neutral conductors which is proportional to the neutral-to-ground conductance; and second trip means connected to said sensing means and responsive to the instantaneous value of said sensing means output signal for producing a trip indication when the instantaneous value of said output signal exceeds a second predetermined reference level.
Claim 17
Dependent Claim
141 words
Ground fault protective apparatus for use on an AC electrical circuit having a line conductor and a neutral conductor, comprising: means for sensing current imbalance on said line and neutral conductors, said sensing means providing an output signal proportional to said imbalance; means for integrating said output signal; first trip means connected to said integrating means for providing a trip indication whenever the output of said integrating means exceeds a predetermined reference; means for inducing a test voltage upon said neutral conductor, whereby a current imbalance is produced between said line and neutral conductors which is proportional to the neutral-to-ground conductance; and second trip means connected to said sensing means and responsive to the instantaneous value of said sensing means output signal for producing a trip indication when the instantaneous value of said output signal exceeds a second predetermined reference level.
Claim 18
Dependent Claim
46 words
Apparatus as recited in claim 12 wherein said induced neutral test voltage comprises a plurality of voltage pulses and said second trip means is responsive to the peak value of output signal pulses produced in response to said voltage pulses upon conditions of high neutral-to-ground conductance.
Claim 19
Dependent Claim
66 words
Apparatus as recited in claim 12 wherein said second trip means is connected to the input of said integrating means and produces a large input signal to said integrating means when said output signal exceeds said second predetermined reference level, whereby the output of said integrating means is caused to exceed said first predetermined level and actuate said first trip means to provide a trip indication.
Claim 20
Dependent Claim
22 words
Apparatus as recited in claim 12 wherein said integrating means is reset after each half cycle of load current through said apparatus.
Claim 21
Dependent Claim
69 words
Apparatus as recited in claim 15 wherein said induced neutral test voltage comprises a plurality of voltage pulses and said second trip means is responsive to the peak value of corresponding current pulses produced by said sensing means upon conditions of high neutral to ground conductance, and said apparatus further comprises means for shaping said output current pulses before applying said output current pulses to said second trip means.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1982-12-24 | 1983-06-25 | 1983-12-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-12-24 | 1987-06-25 | 1987-12-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-12-24 | 1991-06-25 | 1991-12-25 | $7700.00 | Window Closed / Lapsed |